<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style>
.square{ width:200px; height:100px; background-color:#900; margin:100px; position:relative; border-radius:10px;}
.arrow{
	width:0;
	height:0;
	border-width:30px;
	border-style:dashed dashed solid dashed;
	border-color:transparent transparent #900  transparent;
	position:absolute;
	left:50%;
	margin-left:-30px;
	top:-60px;
	
	}
</style>
</head>

<body>
<div class="square">
	<div  class="arrow"></div>
</div>
</body>
</html>
